1. Field of the Invention
The present invention refers to a device to effectuate a digital estimate of a periodic electric signal, to a related method, and a control system for an electric motor, particularly for a bipolar stepper motor, which comprises said device.
2. Description of the Related Art
Stepper motors are known in the state of the art. A typical stepper motor comprises a stator, where there are the windings constituting the phases of the motor, and a rotor including teeth which cause the rotation step.
The stepper motors allow obtaining a high precision control of the movement and for this reason they must have an accurate control system.
A typical control system of a bipolar stepper motor is shown in FIG. 1. A control device 1 controls a power stage of the stepper motor which is constituted by a full-bridge 2 coupled with the supply voltage Vcc and ground. By means of a sense resistance Rs it is possible to obtain a voltage signal Vs proportional to the current flowing through a phase winding of the motor. The voltage signal Vs is compared by means of a comparator 3 with an output signal of a sinusoidal DAC 4. A controller 5 supplies the input signals of the sinusoidal DAC that sets the current level so as to assure a precise peak value of the phase current.
The control system in FIG. 1 has a high circuital complexity due above all to the presence of the sinusoidal DAC and it is not adaptable to the different circuital appliances.